Sensing an opportunity to take advantage of strong polling for tories, PM Teresa May has called a snap general election for June 8, hoping to increase her majority in parliament so she can put through her BREXIT plans and deep budget cuts and other reforms.
Previously the PM had said there would be no election before 2020.

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Nothing underhanded, that is standard election process in the British Parliamentary system. The Prime Minister may call for elections whenever they want. It is quite normal for it to happen when polls are favorable.

“No persons are more frequently wrong, than those who will not admit they are wrong.”
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The underhanded part is that May has been saying since last year that she would not call for a snap election. Can only hope it backfires on her and her party, but I expect the decision was made to do it before any real word gets out on what exit provisions will be negotiated.